Alright, I thought the first time was just bad luck but now it's happening a lot. Pretty much the Danio will swim at the top of the tank with their head touching the top. Their mouth keeps opening and closing and they just putter around. It won't eat but will run away if another fish touches it. Generally this will last a couple days then finally the poor thing will die. All the while the other fish are doing their thing all around the tank. I had three then got six more about 10 days ago. The first one died Monday and when I went home at lunch today, there were two more at the top starting to show the same pattern. I didn't have time to test the water but I tested it last Saturday with no issues. I'm going to test it when I get home this evening. Do I have back luck, or maybe the store in their source? I wanted to get something more expensive this weekend or next week but I rather have this issue solved first. Thanks.